1. Field of the Invention
Embodiments of the invention generally relate to expanding tubulars and well completion. More particularly, embodiments of the invention relate to methods and apparatus for isolating a subterranean zone.
2. Description of the Related Art
Hydrocarbon wells typically begin by drilling a borehole from the earth's surface through subterranean formations to a selected depth in order to intersect one or more hydrocarbon bearing formations. Steel casing lines the borehole, and an annular area between the casing and the borehole is filled with cement to further support and form the wellbore. Flow of hydrocarbons or any other fluid into the wellbore occurs at locations along portions of the casing having openings therein, along a perforated tubular or a screen or along any portions of the wellbore left open or unlined with casing.
The wellbore typically traverses several zones within the subterranean formation. However, some of the zones may not produce hydrocarbons or may produce hydrocarbons at different reservoir pressures. For example, some zones produce water that contaminates the production of hydrocarbons from other zones and requires costly removal from the produced hydrocarbons. Thus, it is often necessary to isolate subterranean zones from one another in order to facilitate the production of hydrocarbons.
Prior zonal isolation assemblies are complex, expensive, and undependable and often require multiple trips into the well at significant time and expense. Prior methods and systems for isolating subterranean zones include the use of packers and/or plugs set within the casing, around the casing or in an open hole section to prevent fluid communication via the casing or the borehole from one zone to another. One method for isolating zones involves expanding a series of solid and slotted casing in the wellbore such that seals on the outside of the solid casing prevent the passage of fluids within the annulus in order to isolate a zone traversed by the solid casing.
However, expansion of solid casing can alter an inner seating surface within the solid casing that is used to isolate the zone, thereby preventing the use of conventional packers that seat inside the solid casing during subsequent completion operations. Further, expanding tubular connections downhole sometimes proves to be problematic due to changes in geometry of the connection during expansion and rotation across the connection caused by use of a rotary expansion tool. Additionally, the type of expander tool suitable for expanding solid tubulars may not be desirable for expanding a sand screen into supporting contact with a surrounding formation. For example, expanding sand screen requires use of significantly less force than when expanding solid tubulars in order to prevent damage to the sand screen. Furthermore, expanding long sections of solid tubulars is time consuming and can be complicated by a short operational life of some expander tools. In addition, factors such as stretching of a running string that an expander tool is mounted on makes it difficult or impossible to accurately determine an exact location downhole for expansion of only a desired portion of selected tubular members.
There exists a need for apparatus and methods for reliably and inexpensively isolating subterranean zones by selectively expanding an assembly of tubulars. Further, a need exists for a zonal isolation assembly that provides a seat for conventional packers used in completion operations.